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Homework Help: Water Bucket problem

  1. Feb 25, 2010 #1
    1. The problem statement, all variables and given/known data

    Is it possible to whirl a bucket of water fast enough in a vertical circle so that the water won't fall out at the top? If the distance from your shoulder to the bottom of the bucket is 0.77 m and the water has a mass of 5.05 kg, what is the minimum speed to whirl the pail?

    2. Relevant equations

    3. The attempt at a solution

    The answer is yes, but to find Vmin?

    I know r = .77m, m = 5.05kg (although shouldn't I have been given the bucket mass also?), so i was thinking

    Fnet = -Fg + Ft = mV^2/r

    but how do i find Ft, or is there no Ft? explain
  2. jcsd
  3. Feb 25, 2010 #2
    You don't need the mass of the bucket because you're concerned about the water. What do you mean by Ft? You're looking for the sum of the forces to come to equilibrium.
  4. Feb 25, 2010 #3
    By Ft I mean tension force exerted by my arm. I didn't think there was any Fn (normal force), right?
  5. Feb 27, 2010 #4


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    Staff Emeritus
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    Homework Helper

    If the bucket is swinging "just fast enough", your arm exerts no force on it at the top of the circle. With that information you can solve your equation,
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